Design and synthesis of glycodendrimers

Multivalent neoglycoconjugates with well-defined structures have considerable potential as inhibitors of cell surface protein-carbohydrate interactions and as tools for studying such recognition processes in vitro. In this review, we outline strategies and synthetic methods for making one such class of neoglycoconjugates based on dendrimers--the so-called glycodendrimers. Glycodendrimers can be classified as: (i) carbohydrate-coated; (ii) carbohydrate-centered; and (iii) fully carbohydrate-based. Approaches to their construction have included both the modification of commercially available dendrimers and de novo dendrimer synthesis. Examples from the authors' and other laboratories are drawn upon to illustrate design considerations and the application of dendritic synthetic principles--including divergent and convergent syntheses--for making glycodendrimers. Key coupling reactions for the synthesis of glycodendrimers include: amide and thiourea formation; glycosylation; photoaddition to allyl ethers; and reductive amination. The advantages and disadvantages of using protected and unprotected saccharide building blocks and potential applications for glycodendrimers in both biotechnology and materials science are also discussed.